TOF camera systems should comprise not only systems that determine distances directly from the time of flight, but in particular also all TOF or 3D-TOF camera systems that extract runtime information from the phase shift of emitted and received radiation. PMD cameras including photonic mixer devices (PMD) are in particular suited as TOF or 3D-TOF cameras, such as are described in, among others, the applications EP 1 777 747, U.S. Pat. No. 6,587,186, and also DE 197 04 496, and which are, for example available from the firm “ifm electronic GmbH” or “PMD-Technologies GmbH” as Frame-Grabber O3D or as CamCube. The PMD camera allows in particular a flexible arrangement of the light source and of the detector, which can be disposed in a housing or also separately. Of course, cameras or devices having at least one receiving pixel should also be included under the term camera or camera system, such as for example the O1D distance measuring device of the applicant.
For determining a distance or a corresponding phase shift of the reflected light, as described in detail in DE 197 04 496, the reflected light is mixed with the modulating signal in the PMD sensor. This mixing delivers an in-phase signal (0°) and a signal shifted by 180°, from which a distance can be determined in a known manner. In order to improve the quality of the distance measurement it can be provided that the transmit modulation is shifted in a targeted manner, for example by 90°, 180°, or 270°, and preferably a phase angle of the reflected determined in relation to the transmitted signal using an IQ (inphase, quadrature) demodulation. This procedure is particularly useful for the extraction of redundant information in order to, for example, compensate for various parasitic effects such as fixed pattern noise (FPN), background light, or asymmetries of the sensor.